/*
 * Copyright (c) 2021, 2022, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * The Universal Permissive License (UPL), Version 1.0
 *
 * Subject to the condition set forth below, permission is hereby granted to any
 * person obtaining a copy of this software, associated documentation and/or
 * data (collectively the "Software"), free of charge and under any and all
 * copyright rights in the Software, and any and all patent rights owned or
 * freely licensable by each licensor hereunder covering either (i) the
 * unmodified Software as contributed to or provided by such licensor, or (ii)
 * the Larger Works (as defined below), to deal in both
 *
 * (a) the Software, and
 *
 * (b) any piece of software and/or hardware listed in the lrgrwrks.txt file if
 * one is included with the Software each a "Larger Work" to which the Software
 * is contributed by such licensors),
 *
 * without restriction, including without limitation the rights to copy, create
 * derivative works of, display, perform, and distribute the Software and make,
 * use, sell, offer for sale, import, export, have made, and have sold the
 * Software and the Larger Work(s), and to sublicense the foregoing rights on
 * either these or other terms.
 *
 * This license is subject to the following condition:
 *
 * The above copyright notice and either this complete permission notice or at a
 * minimum a reference to the UPL must be included in all copies or substantial
 * portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 */
package com.oracle.graal.python.compiler;

import java.util.ArrayList;
import java.util.EnumSet;

/**
 * Block of instructions. Not always exactly like basic block, we allow having jumps in the middle.
 */
final class Block {
    ArrayList<Instruction> instr = new ArrayList<>();
    Block next;
    BlockInfo info;
    /*
     * For exception handlers: allows to unwind more stack items than usual. Useful to rollback to a
     * mid-instruction stack state. Used by `with` statements.
     */
    int unwindOffset;

    // The following fields are filled when assembling
    int stackLevel = -1;
    int startBci = -1;
    int endBci = -1;

    public Block() {
    }

    private static final EnumSet<OpCodes> RETURN_OPCODES = EnumSet.of(OpCodes.RETURN_VALUE, OpCodes.RAISE_VARARGS);

    boolean isReturn() {
        return !instr.isEmpty() && RETURN_OPCODES.contains(instr.get(instr.size() - 1).opcode);
    }

    BlockInfo.AbstractExceptionHandler findExceptionHandler() {
        if (info != null) {
            return info.findExceptionHandler();
        }
        return null;
    }

    int computeLoopDepth() {
        int loopDepth = 0;
        BlockInfo b = info;
        while (b != null) {
            if (b instanceof BlockInfo.Loop) {
                loopDepth++;
            }
            b = b.outer;
        }
        return loopDepth;
    }
}
